1. Field of the Invention
The present invention relates to a simple portable phone built-in portable phone. More particularly, the present invention relates to a simple portable phone built-in portable phone in which degradation of a transmission and reception characteristic can be prevented in antenna switching.
2. Description of the Related Art
A xe2x80x9cmultiple radio terminalxe2x80x9d is known in which a simple portable phone (PHS) is built-in a portable phone (PDC). The multiple radio terminal has a diversity antenna structure which uses a PDC and PHS transmitting and receiving common antenna (hereinafter, to be also referred to as a xe2x80x9cPDC/PHS common antennaxe2x80x9d) and a PDC receive-only built-in antenna. An antenna switching integrated circuit is arranged between a PDC transmitting and receiving section and a PHS transmitting and receiving section.
FIG. 1 is a diagram showing a structure example of the PDC/PHS multiple radio terminal of this type. The PDC/PHS multiple radio terminal is composed of a PDC/PHS common antenna 402 and a PDC built-in antenna 401 as the antenna structure. Also, the PDC/PHS multiple radio terminal is composed of an external terminal 408 and an external terminal 405 as the external input-output terminals. Moreover, the PDC/PHS multiple radio terminal is composed of a PDC receiving section 406, a PDC transmitting section 407 and a PHS transmitting and receiving section 409 as the transmission and reception structure.
The PDC/PHS common antenna 402 is connected with the PHS transmitting and receiving section 409 through a PDC/PHS common filter 404. Also, the PDC/PHS common antenna 402 is connected with the PDC receiving section 406 and the PDC 15 transmitting section 407 through the PDC/PHS common filter 404 and an antenna switching circuit (ANT SW IC) 403. Also, the external terminals 408 and 405 are connected with the PDC receiving section 406 and the PDC transmitting section 407 through the antenna switching circuit 403. The PHS transmitting and receiving section 409, the PDC receiving section 406 and the PDC transmitting section 407 are connected with a control unit 410. Also, the antenna switching circuit 403 is composed of a plurality of switches SW1403A to SW7403G. Each the switches 403A to 403 G is set to the ON/OFF state in response to a control signal from the control unit 410. Thus, the switching control between the antenna and the transmitting and receiving section is carried out.
In such a PDC/PHS multiple radio terminal, an intermittent receiving operation is carried out in the reception wait condition, to eliminate a problem in each signaling system, especially, in case of use on high-speed movement in an area, and in case of use in a underground town area. Also, in such a multiple radio terminal, in the reception wait condition, each operation is not controlled finely, and the PDC side and the PHS side are controlled independently to operate asynchronously. This is because simplification of the circuit structure design and power consumption.
In the PDC/PHS multiple radio terminal as mentioned above, there is a case where the PHS side receives using the PDC/PHS common antenna during the reception in which the PDC side uses a built-in antenna. In this case, the conventional antenna switching circuit disconnects the PDC/PHS common antenna from the PDC receiving section. Therefore, the input/output impedance on PDC side of the PDC/PHS common filter becomes unstable. As a result, the matching condition shifts so that the characteristic of the PDC/PHS common filter becomes worse, resulting in degradation of the transmission and reception characteristic on the PHS side. Therefore, especially, the following problem occurs.
The reception on the PHS side can not be carried out normally at an intermittent reception timing of the PHS side, in the state that the PDC side receives by use of the built-in antenna. As a result, there is a possibility that the synchronization of the reception timing on the PHS side goes out. Also, when the synchronization of the reception timing on the PHS side goes out, the operation to establish the synchronization of the reception timing once again becomes necessary on the PHS side to switch from the intermittent receiving operation to the continuation receiving operation for receiving the terminating call. As a result, the problem is caused that the power consumption increases further with the continuation receiving operation for such synchronous establishment.
In conjunction with the above description, a portable terminal is disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 5-167566). In this reference, the portable terminal is composed of an antenna (1), a receiving section (2), a data clock generating section (3), a first detection notifying section (4), a majority determining section (5), a second detection notifying section (6), and a central processing unit (7). The central processing unit (7) controls the receiving section (2) to stop based on a notice from the first detection notifying section (4) and the receiving section by a notice from the second detection notifying section (6). In this way, when a majority is determined before all data are received, a receiving circuit is stopped without reception of a remainder serial data. When the head of the following data format is detected, the receiving circuit is controlled to start an operation. Thus, low power consumption is realized.
Also, a diversity control method is disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 5-183475). In this reference, in each of n-system base station receiving sections (31, 3N), after a desired signal is extracted from an SD reception signal, the received electric field intensity levels of the desired signals are detected and compared with each other (317). A diversity switching control signal is generated based on the comparing result. A receiving switch section (318) is driven in response to the diversity switching control signal to take out a demodulation signal of the desired signal of a system which has a higher received electric field intensity level. A base station includes n-system base station transmitting section (21, 2N) in addition to the n-system base station receiving sections (31, 3N). A transmission SD antenna is provided for the base station. A base station transmitting section transmits a transmission signal to a mobile station using the transmission SD antenna switched based on the diversity switching control signal from the base station receiving section.
Also, a mobile radio apparatus is disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 5-316018). In this reference, a control data is transmitted from a base station. The control data is received by a receiving circuit (2) via an antenna (1) in a reception waiting state, is demodulated by a digital data demodulating circuit (4), is subjected to a majority determining process by a majority determining circuit (5), and is analyzed by a microprocessor (6). Also, the control data is converted into a digital data by an A/D converter (3). The microprocessor (6) determines the reception electric field intensity of the digital data and determines the number of words to be received within the control data to be repeatedly transmitted. The microprocessor (6) receives only the words of a predetermined number and controls the power source to the receiving circuit to be cut for a time from the head of the remaining words to the next sync signal.
Also, a personal handy phone is disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 8-116301). In this reference, the power supply to a transmitting circuit (3) is turned off and an antenna switch (2) is set to the receiving circuit (5), in a reception waiting mode. A timer circuit (7) is connected to a call identifying circuit (6) and the receiving circuit (5) by a control line (18) to control the power to be intermittently supplied to them. When the mobile phone is called from a base station during the intermittent operation, the identifying circuit (6) stops the timer operation and controls a ringing speaker (12). When a user carries out an off-hook operation, an LAP controller (9) is initiated to establish a link and a TDMA/TDD controller (4) starts the operation. Thus, the handy phone enters a communication mode.
Also, a radio apparatus is disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 9-27782). In this reference, a radio section (12) includes a receiving section for demodulating a receive data from a radio wave received by an antenna (11). A power supply control unit (14) controls the supply of power source (13) to the radio section (12) in an ON/OFF mode. A first timer (15) is set with a period of the ON/OFF control by the power supply control unit (14). A second timer (16) is set with a time longer than the ON time of the first timer (15). A control unit (20) controls the respective sections, and switches from the first timer (15) to the second timer (17) to allow the receiving section to receive data for longer time.
An object of the present invention is to provide a multiple portable phone in which the degradation of transmission and reception characteristic on a PHS side through an antenna switching operation on a PDC side can be prevented.
Another object of the present invention is to provide a multiple portable phone of a PDC side diversity system in which the suppression of power consumption and the prevention of going-out of synchronization in an intermittent receiving operation are made possible.
In order to achieve an aspect of the present invention, a multiple portable phone includes a first antenna for a first communication system, a second antenna common to the first communication system and a second communication system, and a switching circuit controlled based on a control signal. The multiple portable phone further includes a receiving circuit provided for the first communication system, and connectable to the first and second antennas via the switching circuit, and a transmitting and receiving circuit provided for the second communication system, and connectable to the second antenna, and an impedance matching circuit connected to the switching circuit. A control unit generates the control signal to control the switching circuit to connect the impedance matching circuit to a path from the second antenna to the transmitting and receiving circuit when the transmitting and receiving circuit carries out a receiving operation using the second antenna while the receiving circuit carries out a receiving operation using the first antenna.
The multiple portable phone may further include a common filter of a low pass filter and a band pass filter. In this case, the receiving circuit may be connected to the second antenna via the switching circuit and the low pass filter in response to the control signal, and the transmitting and receiving circuit may be connected to the second antenna via the band pass filter.
Also, the control unit controls the receiving circuit while generating the control signal, such that the receiving circuit carries out an intermittent receiving operation in a first predetermined time interval as the receiving operation while one of the first and second antennas is selected. In this case, the control unit may control the transmitting and receiving circuit while generating the control signal, such that the transmitting and receiving circuit carries out an intermittent receiving operation in a second predetermined time interval as the receiving operation using the second antenna. Also, the control unit may control the intermittent receiving operation of the receiving circuit and the intermittent receiving operation of the transmitting and receiving circuit to be independent and asynchronous.
Also, the multiple portable phone may further include a transmitting circuit provided for the first communication system and connectable to the first and second antennas via the switching circuit. In this case, the switching circuit may include first and second switches operatively connectable the receiving circuit to the first antenna. In addition, the switching may further include third and fourth switches operatively connectable the transmitting circuit to the first antenna via the first switch, wherein a node between the third and fourth switches is operatively connected to the second antenna, and a fifth switch operatively connectable the impedance matching circuit to the second antenna via the first switch. The first to fifth switches are controlled in response to the control signal. Moreover, the switching circuit may further include a sixth switch connected between a first external terminal and a node between the second switch and the receiving circuit. In this case, the sixth switch is controlled in response to the control signal. Also, the switching circuit may further include a seventh switch connected between a second external terminal and the node between the second switch and the receiving circuit, and an eighth switch connected between the second external terminal and a node between the fourth switch and the transmitting circuit. In this case, the sixth to eighth switches are controlled in response to the control signal.
The impedance matching circuit may have substantially the same impedance as the receiving circuit. Also, the first communication system may be a PDC system and the second communication system may be a PHS system. In addition, the first antenna may be built in the phone.
In another aspect of the present invention, an antenna switching method in a multiple portable phone is attained by (a) selectively connecting a receiving circuit for a first communication system to one of a first antenna and a second antenna via a switching circuit for a receiving operation of the receiving circuit; by (b) connecting a transmitting and receiving circuit for a second communication system to the second antenna for a receiving operation of the transmitting and receiving circuit; and by (c) compensating impedance change depending on the switching circuit.
The (a) step may be attained by connecting the receiving circuit to the second antenna via the switching circuit and a low pass filter, and the (b) step may be attained by connecting the transmitting and receiving circuit to the second antenna via a band pass filter.
The (c) step may be attained by selectively connecting an impedance matching circuit to a path from the second antenna to the transmitting and receiving circuit for the receiving operation of the transmitting and receiving circuit. In this case, the (c) step includes: connecting the impedance matching circuit to the path from the second antenna to the transmitting and receiving circuit when the transmitting and receiving circuit carries out the receiving operation using the second antenna while the receiving circuit carries out the receiving operation using the first antenna.
Also, the receiving operation of the receiving circuit is an intermittent receiving operation in a first predetermined time interval while one of the first and second antennas is selected. The receiving operation of the transmitting and receiving circuit is an intermittent receiving operation in a second predetermined time interval using the second antenna. The intermittent receiving operation of the receiving circuit and the intermittent receiving operation of the transmitting and receiving circuit may be independent from each other and asynchronous with each other.
Also, it is desirable that the impedance matching circuit has substantially the same impedance as the receiving circuit. Also, the first communication system is a PDC system and the second communication system is a PHS system.